Shock absorbing strut



May 26, 1936. K. w. WARREN SHOCK ABSORBING STRUT Filed Feb. 9, 1933 2Sheets-Sheet 1 INVENTOR. KIN/V67 M h ARRHY A TTORNEY May 26, 1936.. K.w. WARREN SHOCK ABSORBING STRUT 2 Sheecs-Sheet 2 Filed Feb; 9, 1933 lll0 8 M w Q M &m in .mm

- IN VEN TOR. /(/VA E7// W MF/ffA/ ATTORNEY Patented 'May 26, 1936UNITED STATES PATENT OFFlCE SHOCK ABSQRBING STRUT .Konneth W. Warren,South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend,Ind., a corporation of Delaware Application February 9, 1933, Serial No.656,005 I 11 Claims. (01. 267-64) This invention relates to shockabsorbers and more particularly to hydraulic pneumaticshdck absorbingstruts for aeroplanes.

Broadly the invention comprehends a shock absorbing strut for aeroplanesincluding hydraulic and pneumatic resistance means arranged so that thehydraulic means dissipates the larger part of the impact energy onlanding an aeroplane, while the pneumatic resistance means takes thetaxiing loads.

An object of the invention is to provide a shock absorbing strut for anaeroplane including but few parts arranged to provide the minimum lengthand yet permit ofthe attachment of lugs or braces to take side loads atthe lowest possible point which-is not movable with respect to theaeroplane.

Another object of the invention is to provide a shock absorbing strutfor an aeroplane including a jacketed shock absorber of the hydraulicpneumatic type wherein the fluid and air or gas flow freely from ahollow piston rodto the jacket and from the jacket to the hollow pistonrod.

Another object of the invention is to' provide a 5 shock absorbing strutfor aeroplanes in which the amount of required machine operation on theparts during manufacture shall be materially reduced.

A further object of the invention is-to provide a shock absorbing strutfor an aeroplane having great resistance against side loads and whereinthe surface slidably in contact with the packing gland is totallyenclosed.

A still further object is to provide a pneumatic hydraulic shockabsorbing strut for an aeroplane having great resistance against bendingloads and in which the air pressures necessary are considerably reduced.I Yet a further object of the invention is to pro- 0 vide a shockabsorbing strut for an aeroplane which has the advantage of a shortlength, is highly eilicient in operation'and yet of marked simplicity asa whole and in respect to each of its composite parts, so thatitsmanufacture may 5 be economically. facilitated both as regards its partsand assembly.

Other objects of the invention will appear from the followingdescription taken in connection with the drawings, which form a part ofthis 0 specification, and in which:

Figure 1 is 'a vertical sectional view of a shock absorbing strutembodying the invention;

Figure 2 is a cross-sectional view substantially in line 2--2, Figurel;it Figure 3 is a vertical sectional view of a slightly is threaded toreceive a packing nut 24.

modified form of shock absorbing strut embodying features of theinvention; and

Figure 4 is a sectionalview-oi" a modified flap valve constructionadaptable to the structures of Figures 1 and 3.

Referring to the drawings for more specific de-' tails of the invention,I0 represents a casing on a jacket closed at one end by a 'cap' l2having a clevis I4 on the top thereof for' attaching the strut to thefuselage of an aeroplane. also has a sleeve l6 extending into the casingconcentrically with respect to the wall thereof,

' The other end of the casing has a packing chamber l8. The inner end ofthe packing chamber has a shoulder -on which is seated a packing 15 ring22 and the other end of the packing chamber As shown, the packing nut iselongated and is piloted well into the packing chamber to lend strengthand rigidity thereto, and arranged in the packing 2o chamber are packingglands 26 compressible between the packing-ring 22 and the packing nut24.

The outer wall of the packing chamber has formed thereon a plurality oflugs 28 to which brace members, not shown, may be attached, and suitablysecured in the wall of the casing l0 adjacent the cap i2 is a shortsleeve 80' internally threaded toreceive a valve 32 through which thestrut may be filled with suitable hydraulic fluid and air or gas underpressure.

A hollow cylinder piston 34 is suitably secured at one end thereof tothe sleeve [6, and secured on the other end of the piston is a pistonhead 36. The piston has a plurality of openings 38 providing for freeflow" of fluid and air or gas fromthe piston to the casing andfrom thecasing to the piston. v

The piston head has a double diametral bore 40. A case-hardened plate 42having a metering orifice 44 is'fitted in the bore having the largerdiameter, and supported on the back of the piston head in registrationwith the bore having the smaller diameter is a snubbing cylinder 46.

' As shown, the snubbing'cylinder 46 has a circumferential flange 48 onthe end thereof abutting 4,5 the back of the piston head, and screws 50passed through the flange, the piston head, and the case-hardened platesecurely fasten these parts together. The other end of the cylinder 46is provided with a. flap valve 52 arranged to provide 50 maximum flow offluid through the cylinden The snubbing cylinder is further providedwith small openings 54 in the wall thereof adjacent the flange 48.

A cylinder 56 is positioned for reciprocation The cap 2 I the packinggland and between the walls of other endof the cylinder is closed by acap 60 supporting a metering pin 62 for cooperation with the orifice 4|in the case-hardened plate ii. The cap has on the top thereof a clevis64 for attaching the strut to the axle of an aeroplane.

The modified form of Figure 3 is similar in construction to that ofFigure 1 except that the packing is carried upon the internaltelescoping or moving cylinder thereby'permitting complete enclosure ofthe surface upon which the packing slides, and completely preventingaccumulation of dirt, grit and foreign substances which might in timetend to cause leakage.

As shown, the strut comprises a cylindrical casing-member i-lll closedat its upper end by 'a cap "2 and carrying an outer bearing collar-member III at its lower end, into which a second cylindricalcasing-member H6 is telescopically arranged. To prevent leakage betweenthe members, a series of packing rings H1 is carried on the secondmember 6 between a fixed inner bearing collar H8 and a loosely mountedretaining ring I20 which isheld in place by engage- .ment with a sleeveI24 threaded on the latter cylindrical member 6, and which forms anadjustable'shoulder I22 for said retaining ring. A

sleeve I26 set of the cylindrical casing member lill rests at one endupon the collar H4 and forms a shoulder at its other end against whichthe retaining ring I may strike, thereby providing a stop to limit theminimum distance between the inner collar Ill and the outer collar Ill,so that a certain amount of overlap of the cylindrical memberssufllcient to withstand bending loads is always assured. As the sleeveit acts on the retaining ring, there is a tendency for the packing II Itoact as a cushion when the cylindrical-members are fully extended, andalso the packing is more highly compressed which assures against leakagewhenthe members are in the extended or idle position.

As in the form of Figure 1, a hollow cylinder l3! concentric with theouter cylindrical member II. and secured to the end cap H2 carries atits lower end a piston I which is provided with a suitablehardmetal'bushing ll. Secured to a lower endcap member I42 which iscarried by the lower end of the cylindrical telescopic member H6 is ametering pin I of varying cross section, which is adapted to cooperatewith the orifice I38. concentrically mounted over the orifice I3! is atubular member I having small side orifices I and a .valve ISI coveringthe top which is adapted'to per'mit flow of shock tion permits free flowof fluid pasing upward through the orifice |3l but restricts thereturnflow by causing the fluid to pass through the side oriflm Ill therebyrestricting'rebound."

- In order that the entire area-o1 theouter cylinder may be effective toresiliently support the load, for as during thereby'pennittinglowerpressuresinthesh-utthemner cylindrical member I3! isprovidedwith a pluralityof ports IS! in rdier that free communicationis-maintained between the inside and the outside of the cylindricalmember'lll- W As shown in Figure 4, the central tube I of Figure 3 maybedispensed with and a diaphragm only. This construc- I" containing aone-way valve it! may be directly inserted into the cylindrical-memberIll. In such an arrangement side orifices I for controlling rebound areplaced preferably at the base of the cylindrical member I34, and portsI52 for the free communication between the inside and the.outside-.ofthecylindrical member l3 are restricted to the portion above the diaphragmI60.

Assuming that either strut, both of which are 1 shown in a fullyextended position, is filled with a suitable hydraulic liquid and air orgas under pressure, then the strut will under impact -of landing causethe hydraulic liquid to be forced through the metering orifice past themetering 1 pin into the upper part of the strut where the air or gaswill be compressed by the rise of the liquid and this combinedresistance oflered by the compression of the air or gas and the flow ofthe liquid produces the work curve desired. 2

On the compression stroke the liquid passes freely through the flapvalve on top of the snubbing cylinder Ii, into which the metering pin.extends, as in Figures 1 and 3 or through the diaphragm as in'Figure 4,into the hollow piston 2; and from the hollow piston into the casing orjacket. vOn the return stroke the flap valve closes, due to the pressureof the compressed air or gas, forcing the liquid to return from thecasing or jacket to the hollow piston and from the piston 3( through thesmall openings near the bottom of the snubbing cylinder, or thecorresponding openings I of Figure 4, and thence through the meteringorifice N to the cylinder 56, thus preventing the sudden rebound thatwould other- 35 wise result.

While the preferred embodiments of the invention have been described, itis to be understood that these are given merelyas an example of theunderlying principles of the invention and since these may beincorporated in other specific mechanical structures, 1' do not intendto be limited to those shown exceptas such limitations are clearlyimposed by the impending claims.

Having thus described the various features of 45 the invention, what Iclaim as' new and desireto secure by letters Patent is:-

LAshockaMorbingstl-utdomprising acasing, a hollow piston supported andfixed concentrically therein, a head on the lower end of the 50 pistonhaving an orifice, a cylinder supported ontheheadwithinthepistonregisteringwiththe orifice, and a flap valve mrthe other end of the cylinder permitting flow upward therethrough.

2. A shock absorbing strut comprising a casing, a .hollow perforatedpiston rod supported andfixedconcentricallymaheadonthe lower end of thepiston having an orifice, a cylinder supported on the headconcentrically within the piston, and a valve'onihe cylinder permit- 60andameteringpin-inthemcillncatingcmmber adaptalfleior cooper-am with themetering orifice.

4.Aahoc kabsoriflngstmtoulnprlsingacas-. ingaclosureononeemiottheuinm'apaek-is.

ing chamber on the other end of the casing, a packing ring in thepacking chamber, a hollow perforated piston fixed to the closureconcentrically within the chamber, a head on the piston having ametering orifice, a check valve associated with said orifice to restrictreturn of flow therethrough, a cylinder positioned for reciprocationbetween the casing and the piston, a collar on the cylinder adapted toen age the packing ring, and a metering pin carried by the cylinder forcooperation with the metering orifice.

5. A shock absorbing strut comprising a casing, a closure on one end ofthe casing, a packing chamber on the other end of the casing having ashoulder on the inner end and threaded at the outer end, a packing ringsupported on the shoulder, a packing nut threaded into the open end,packing material between the packing ring and the packing nut, a hollowperforated cylinder fixed to the closure concentrically within thecasing, a head on the piston having a concentric metering orifice, acheck valve associated with said orifice to restrict return of fiowtherethrough, a cylinder positioned for reciprocation between the innerwall of the casing and the outer wall of the piston, a collar on thecylinder adaptable for engagement with the packing ring, and -a meteringpin carried by the cylinder for cooperation with the metering orifice.

6. A shock absorbing strut comprising a casing, a closure-on one end ofthe casing, a sleeve on the closure extending concentrically into thecasing, a hollow perforated piston having one of its ends secured to andfixed on the sleeve,.a piston head secured to the other end of thepiston and provided with a concentric orifice, a snubbing cylinderwithin said hollow perforated piston having one end secured to the backof the head, a flap valve on the other end of the snub bing cylinder, acylinder positioned for reciprocation between the inner wall of thecasing and the outer wall of the piston, and a metering pin carried bythe piston adaptable for cooperation -with the metering orifice.

7. A shock absorbing strut comprising a casing, a closure on one end ofthe casing having a sleeve extending concentrically into the casing, apacking chamber on the other end of the casing having a shoulder in oneend and internally threaded at its other end, a packing ring seated onthe shoulder, a packing nut threaded in the open end of the chamber,packing material between the packing ring and packing nut, a hollowperforated piston rod supported by and fixed on the leve within thecasing, a head on the piston rod. having a concentric metering orifice,a snubbing cylinder within said hollow perforated piston secured by oneof its ends to the back of the piston head, a fiap valve on the otherend of the snubbing cylinder, a cylinder positioned for reciprocationbetween the inner wall of the casing and the outer wall of the piston, acollar on the cylinder for engagement with the packing ring, and ametering pin carried by the cylinder for cooperation with the meteringorifice.

8. A shockabsorbing strut comprising a casing,

- a closure for one end of the casing including a cap having a sleeveextending concentrically within the casing and a clevis on the top ofthe cap, a packing chamber on the other end of the casing having ashoulder at its inner end and threaded at its outer end, a packing ringseated on the shoulder having a part extending laterally within thecasing, a packing nut threaded in the chamber having an unthreaded partextending inwardly, packing material in the chamber between the packingring and the packing nut, a hollow perforated piston secured to thesleeve on the closure and extending concentrically within the casing, ahead secured to the piston having a concentric metering orifice, asnubbing cylinder within said perforated piston having one of its endssecured to the back of the head, a flap valve on the other end of thesnubbing cylinder, a cylinder positioned for reciprocation between theinner wall of the casing and the outer wall of the piston, a collar onone end of the cylinder engageable with the-packing ring, a closure onthe other end of the cylinder including a cap having a clevis, and ametering pin supported by the cap for cooperation with the meteringorifice.

9. A shock absorbing strut comprising a casing, a closure on one end ofthe casing, a sleeve on the closure extending concentrically into thecasing, a hollow piston having one of its ends secured to the sleeve, apiston head secured to the other end of the piston and provided with acentral orifice, a snubbing diaphragm secured within the hollow piston,a fiap valve thereon, a cylinder positioned for reciprocation betweenthe inner wall of the casing and the outer wall of the piston, and ametering pin carried'by the piston adaptable for cooperation withthe-orifice.

10. A shock absorbing strut comprising a casing, a closure on one end ofthe casing, a sleeve on the closure extending concentrically into thecasing, a hollow piston having one of its ends secured to the sleeve, apiston head secured to the other end of the piston and provided with acentral orifice, a snubbing diaphragm secured within the hollow piston,a fiap valve thereon, perforations in the wall of the hollow pistonabove the diaphragm, a cylinder positioned for reciprocation between theinner wall'of the casing and =the outer wall of the piston, and ametering pin carried by the piston adaptable for cooperation with theorifice, saidfiap valve being located a distance from said piston headsubstantially the length oi said metering pin.

' 11. A shock strut comprising a pair of concentric. cylinders securedand capped at one end, a telescopic cylinder mounted for reciprocationbetween said concentric cylinders, a bearing collar mounted on the endof the telescopic cylinder and adapted to engage the inner wall of theouter cylinder, a bearing collar on the end of the outer cylinderadapted to engage the outer surface of the telescopic cylinder, a sleevepositioned on Y said second named collar between said outer cylinder andtelescopic cylinder, and a packing retained on said telescopic cylinderin position against said first named collar, said packing adapted toengage said sleeve and limit the maximum extending movement of the shockstrut.

. KENNETH W. WARREN.

